A 9-year monitoring study of diseases on potato seed tubers imported to Israel

Potato seed tubers are imported annually to Israel from northern Europe. Although the seed is registered as certified, a survey carried out over a 9-year period indicated that most lots were affected by latent or active bacterial and fungal infections. Latent infection byErwinia carotovora subsp.atroseptica, the causal agent of blackleg, at a level of 10³ cells/g peel, was present in 30% of the lots in most years. Black scurf caused byRhizoctonia solani was present in 20–70% of the imported lots, with a moderate to high level of infection in all years except 1985. In contrast, although many lots were affected by powdery scab, common scab, and Fusarium dry rot in most years, disease incidence within lots was generally low. The gangrene pathogen (Phoma exigua) was rarely detected. The survey findings are of marked importance, due to the extensive use of soil fumigation in Israeli agriculture.     

EMPHYSEMATOUS PYOMETRA IN A DOG

An 8-year-old intact female West Highland White Terrier was examined for anorexia, vomiting, abdominal distension, and mild purulent vulvar discharge. The results of physical examination, laboratory testing, and radiography are presented. Emphysematous pyometra was suspected and confirmed at surgery. Clostridium perfringens was isolated from the uterine lumen. A brief discussion of emphysematous pyometra is presented.     

Detection ofClostridiue chauvoein in formalin-fixed,paraffin-embedded tissues of sheep by the peroxidase-antiperoxidase (PAP) technique

A peroxidase-antiperoxidase (PAP) technique was used to detectClostridium chauvoei in tissue sections from sheep inoculated intramuscularly with a pure culture of this microorganism. Samples of various tissues were taken for bacteriology, histopathology and immunohistochemistry. A primary antiserum againstC. chauvoei for use in the PAP technique was produced in rabbits. Formalin-fixed, paraffin-embedded sections of muscle samples were positively and specifically stained by the PAP technique. The results were consistent with those obtained by bacteriology, but the PAP test was simpler, quicker and less expensive than the bacteriological procedures.The use of the PAP technique would be appropriate for detecting clostridial infections without the constraints of conventional identification methods, especially where laboratory conditions for anaerobic procedures are not readily available.Abbreviations HE haematoxylin and eosin - NS normal rabbit serum - P-ab primary antibody - PAP peroxidase-antiperoxidase - PBS phosphate-buffered saline     

邵阳某地黄牛气肿疽暴发流行的诊治报告

１９９８年湖南省邵阳市某地暴发流行一种牛的疫病，根据流学调查，症状，病理变化和细菌学检查，确诊为黄牛气肿疽病。采取台措施以及青霉素和磺胺药治疗，有效地控制了疫病的流行。     

EMPHYSEMATOUS CHOLECYSTITIS IN THE NONDIABETIC DOG: THREE CASE HISTORIES

Emphysematous cholecystitis not associated with diabetes mellitus was diagnosed in three dogs. All three dogs were examined because of vomiting. Neutrophilia, elevated serum alkaline phosphatase, and normal serum glucose were present in each animal. A gas-filled gallbladder and pericholecystic gas were seen radiographically in all three dogs; a cholecystolith was present in one dog. A cholecystectomy was performed on two dogs. Cultures of bacteria from these two bladders revealed Clostridium sp. One of these dogs was euthanized because of acute renal tubular necrosis that was diagnosed after ten days of treatment with gentamicin. The second dog recovered without incident. The third dog was treated successfully with antibiotics.     

Contamination of healthy seed tubers byPolyscytalum pustulans andPhoma exigua var.foveata in potato stores

Summary Between 1976 and 1981, healthy seed tubers were kept in five stores used for holding virustested stem cutting stocks. The incidence ofPolyscytalum pustulans (skin spot) andPhoma exigua var.foveata (gangrene) was assessed after four months storage. The tubers were planted, often after various treatments, and the incidence of the pathogens on their progeny tubers assessed after harvesting and further storage. Seed tuber contamination byP. pustulans varied with the store and the differences were reflected in the incidences of contamination on their progeny tubers. Progeny tuber contamination byP. pustulans was not affected by fumigation of the seed tuber with 2-aminobutane but was reduced by dipping seed tubers just prior to planting in either a surface disinfectant or thiabendazole. Seed and progeny tuber contamination byP. exigua var.foveata was not affected by storage site or by chemical treatment just prior to planting.

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Zusammenfassung Zwischen 1976 und 1981 wurden gesunde Pflanzknollen in fünf L?gern gehalten, die zum Aufbewahren virusgetesteter ‘stem cutting”-Best?nde dienten. Nach viermonatiger Lagerung wurde das Auftreten vonPolyscytalum pustulans (Tüpfelfleckenkrankheit) undPhoma exigua var.foveata (Phoma-F?ule) ermittelt. Die Knollen wurden nach oft unterschiedlicher Behandlung angepflanzt und das Vorkommen der Pathogene an den Tochterknollen nach Ernte und weiterer Lagerung festgestellt. Die Versuche wurden mit Pflanzknollen durchgeführt, die in der ‘DAFS nuclear stock farm” erzeugt wurden. Die Pathogene wurden lediglich an den Knollen des Anbaus von 1977 nachgewiesen, und dies auch nur in sehr geringem Masse (Tabelle 1). Der Befall der Pflanzknollen war w?hrend der Lagersaison 1976/77 im Lager C am h?chsten und im Lager A am niedrigsten (Tabelle 2). In gleicher Weise variierte mit der Lagerung der Befall der Tochterknollen, wenn auch für die Sorte Kerr's Pink der Unterschied zwischen den L?gern B und C nicht signifikant war. Der Umfang desP. pustulans-Befalls war an den Tochterknollen signifikant (r=0,84; 22 d.f) bezogen zum Vorkommen der Tüpfelflecken. Zwei weitere Experimente best?tigten, dass der Knollenbefall mitP. pustulans mit dem Lager variierte (Tabelle 3). Die Kontamination der Tochterknollen wurde nicht durch die Begasung der Pflanzknollen mit 2-Aminobutan bei der Ernte beeinflusst. In zwei Versuchen wurde der Befall der Tochterknollen mitP. pustulans reduziert, in dem die Pflanzknollen aus Lager C entweder in Oberfl?chen-Desinfektionsmittel oder in ein Fungizid (Thiabendazol) getaucht wurden (Tabelle 4). Dieses Ergebnis best?tigte sich in zwei weiteren Versuchen, in denen Pflanzknollen der L?ger A, C und L verwendet wurden (Tabelle 5). Der Befallsumfang der Pflanz- und Tochterknollen mitP. exigua var.foveata wurde vom Lager, in dem sich die Knollen befanden, nicht beeinflusst (Tabellen 2 und 3). Die Kontamination der Tochterknollen wurde auch nicht durch die chemische Behandlung kurz vor dem Pflanzen berührt (Tabellen 4 und 5). Im Gegensatz zu diesen Versuchen, bewirkte das Best?uben der Pflanzknollen mit trockener, kontaminierter Lagererde einen h?heren Befallsgrad der Tochterknollen als das Best?uben mitP. exigua var.foveata freier Erde (Tabelle 6). Diese Ergebnisse wurden in Bezug zu einem luftbürtigen Inokulum diskutiert, das man von einem in Kartoffell?gern vorkommenden kontaminierten trockenen Boden erhielt (Carnegie et al., 1978).

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Résumé Entre 1976 et 1981, des plants sains ont été conservés dans 5 locaux utilisés pour la conservation des stocks issus de boutures indemnes de virus. La fréquence dePolyscytalum pustulans (Oosporiose) et dePhoma exigua var.foveata (Gangrène) a été notée après 4 mois de conservation. Les tubercules ont été plantés, souvent après divers traitements, et l'incidence des parasites sur leur descendance évaluée après récolte puis après conservation. Les expériences ont été conduites en utilisant des plants en provenance de la station DAFS produisant le matériel de base. Les parasites n'ont été détectés que sur des tubercules de la récolte 1977, et à un niveau très bas (tableau 1). La contamination des plants parP. pustulans, pendant la période de conservation 1976–77 est la plus importante pour le magasin C et la plus faible pour le magasin A (tableau 2). La contamination des tubercules fils varie de la même fa?on, en fonction du local de stockage, bien que la différence entre les locaux B et C ne soit pas significative pour la variété Kerr's Pink. Sur les tubercules fils, la fréquence de la contamination parP. pustulans et la fréquence de l'Oosporiose sont significativement corrélés (r=0,84; 22 d.f.). Deux autres expériences confirment que la contamination des tubercules varie avec le local de stockage (tableau 3). La contamination des tubercules fils n'est pas modifiée par la fumigation des plants à la récolte par le 2 aminobutane. Dans deux essais, la fréquence de la contamination des tubercules fils parP. pustulans est réduite par le trempage des tubercules de semences venant du local C soit dans des désinfectants superficiels soit dans un fongicide, le thiabendazole (tableau 4). Ce résultat est confirmé par deux autres essais ultérieurs utilisant des plants provenant des locaux A, C et L (tableau 5). La fréquence de la contamination des plants et des tubercules fils parP. exigua var.foveata n'est pas modifiée par la nature du local dans lequel les plants ont été conservés (tableaux 2 et 3). Parallèlement, la contamination des tubercules fils n'est pas modifiée par un traitement chimique appliqué juste avant plantation (tableaux 4 et 5). Par opposition à ces données expérimentales, le saupoudrage des plants avec de la terre sèche contaminée prélevée dans un local, conduit à une augmentation de la contamination de la descendance, comparée à un saupoudrage effectué avec de la terre indemne deP. exigua var.foveata (tableau 6). Ces résultats sont discutés en se référant à l'inoculum aérien provenant de la terre sèche contaminée présent dans les locaux de stockage (Carnegie et al., 1978).

     

A rapid scoring technique for potato tuber disease assessment

Summary Three methods of scoring disease severity were compared on potato tubers infected with either common scab, gangrene or dry rot. For each disease, replicated samples of infected tubers were taken of 12–14 cultivars representing a range of reaction from resistant to susceptible, and disease severity assessed by 1) estimating the proportion of the surface area affected by the disease, 2) calculating the percentage of tubers infected to a pre-determined amount, 3) an overall ‘glance score’ on a 1–9 scale of decreasing infection. The third method gave scores which correlated closely with the others, and since it is direct and simple to use, it has become the preferred method in disease screening tests at the Scottish Crop Research Institute.     

Comparison of the interactions ofErwinia carotovora ssp.atroseptica withPhytophthora infestans, Phoma foveata andFusarium coeruleum in rotting potato tubers

Summary An interaction betweenP. infestans andE. carotovora subsp.atroseptica (Eca) in rotting tubers was confirmed and the biochemical basis for its occurrence investigated. The pH of tissue infected withP. foveata became alkaline whereas tissue infected withP. infestans orF. coeruleum did not rise above neutrality, which could promote pathogenicity of Eca by maintaining pH closer to the optimum for polygalacturonase activity. Polygalacturonase, pectate lyase and galactanase were detected in cultures of all three fungi grown on media containing cell wall material or pectin from tubers. AsP. infestans produced more polygalacturonase than the other two fungal tuber rot pathogens the possibility was investigated that oligogalacturonide products of enzymatic degradation of pectin byP. infestans stimulates pathogenicity of Eca. However, while tubers soft-rotted after infiltration with supernatant from fungal cultures grown on tuber cell wall material, controls showed that rotting resulted from infiltration rather than the products contained in the infiltrated water.     

Variation in pathogenicity among isolates ofPhoma exigua var.foveata on potato cultivars differing in resistance

Summary The size of gangrene lesions on potato tubers was significantly affected by isolate ofPhoma exigua var.foveata and cultivar. Inoculation methods based on the introduction of a wheat-germ/sand culture into the peripheral tissues of the tuber revealed greater differences among isolates and cultivars than one involving a deeper insertion of a mycelium/potato dextrose agar plug. The method of testing influenced the order of ranking of certain isolates and cultivars. The relative pathogenicity of isolates was similar over two years, but no cultivar-isolate interactions were found.